In the driveline of an automotive vehicle, an engine is usually connected through a transmission to drive the wheels of the vehicle. As the vehicle velocity changes from zero to a normal cruising speed, there are attendant changes in the engine operation and the transmission ratio. For example, as the driver signals a demand for greater torque by depressing the accelerator pedal, this can open the carburetor to provide additional fuel to the engine cylinders. As the vehicle speed increases, the tranmission is generally shifted through several gear ratios until cruising speed is reached. With the increased use of electronic circuits, and especially with the advent of integrated circuits, the amount and precision of electronic control have begun to increase substantially.
To effect more precise and more efficient control of the engine and/or transmission, various sensors have been used to derive information such as engine manifold pressure, engine temperature, the temperature of the engine coolant, the angular velocity of the engine (or transmission) output shaft, the torque supplied over this output shaft, and so forth. These various data signals can then be combined in a processing arrangement which compares the actual system operation to the desired operation, and controls the engine operation to reduce the disparity between the actual and desired operating conditions. Recently it has been found that output torque can be derived by measuring the acceleration of the engine crankshaft. This provides useful data for any control system requiring an indication of the torque actually produced. In general such a torque signal has been provided by averaging the torque present in the shaft over a measuring interval.
It now appears that some system for measuring torque non-uniformity is desirable. By non-uniformity is meant the deviation of the torque from a periodic, or generally constant, value under steady state operation. While an indication of torque non-uniformity has more limited application in the United States at the present time, because of the use of stoichiometric operation and catalytic converters, the "lean burn" strategy employed for the engine control of many European vehicles can now use the indication of torque non-uniformity. The more efficient operation obtained using excess air in a lean burn system can produce excessive unburned hydrocarbons, which excess is correlated with non-uniform values of the driveline torque. Hence a signal denoting torque non-uniformity can be utilized for effective control of a lean burn engine to obtain maximum efficiency and still avoid excessive unburned hydrocarbons in the engine exhaust.
It is therefore a prime consideration of the present invention to provide an effective system for indicating non-uniformity of the driveline torque.
A corollary consideration is to provide such a system which utilizes the torque non-uniformity signal in the control of the engine, or transmission, or some other adjustable unit in the driveline.